The Role of Gas in
Galaxy Dynamics

Motivation

Recent surveys are revolutionizing our understanding of galaxies. New IFU surveys such as SAMI, MaNGA, and CALIFA, along with new facilities like ALMA and MUSE, are collecting kinematic data of thousands of galaxies in the nearby universe revealing new properties about the morphologies, dynamics and kinematics of galaxies. Future facilities, such as the ASKAP and the SKA promise a significant advance in the quality of data available. At the same time, advances in computational cosmology have led to improved predictions for the properties of galaxies in the current paradigm of structure formation, the Lambda Cold Dark Matter model. The simultaneous progress in the modeling and observing fronts has transformed the field of galaxy dynamics into a powerful probe of both cosmology and galaxy formation. Gas is an important driver of the evolution of galaxies, both at high redshift where it is by mass a major contributor and at low redshift where its strong coupling to the stellar component determines the evolution of morphology, star formation, radiation field and kinematics.

Although some progress has been made in the last few years in understanding the role of gas in galaxy formation and evolution we are still left with many questions and challenges. For instance, gas is thought to flow into galaxies via cold accretion dominating at low mass and hot accretion dominating at high mass. What is the evidence for cold and hot flows? Are M* galaxies surrounded by hot coronae and which tracers are best to determine their presence? Once it condenses at the center, gas can form stars and subsequently be blown out by supernovae explosions (and perhaps AGN feedback), carrying with it the yields of the massive stars. The gas is then thought to either escape, enriching the intergalactic medium, or rain back on the galaxy. How does the circulation of gas in galaxies occur? The evidence of this cycle and its modeling is fundamental to our understanding of galaxy formation.

Gas in galaxies is often warped, exhibits holes, and is transported by dynamical structures such as bars and spirals. How does the condensation of gas affect the kinematic properties of disks? How is gas transported within disks by bars and spirals, and what does this tell us about the mass distribution of galaxies? Where does gas settle and what is the relation to the structure of the disks? Are warps related to the inflow of gas or to the environmental perturbations?

At high redshift gas plays an important role in shaping the morphologies of galaxies and, once escaped, in enriching the intergalactic medium. Making explicit connections between the high and low redshift Universe holds the promise of validating or challenging the cosmological paradigm of structure formation on galactic scales.

A final connection is made to the Milky Way, which is the ideal target for studying galaxy formation. What do atomic and molecular gas reveal about the structure of the bulge and disk of the Milky Way? Which tracers can be used to trace fountain activity in the Milky Way? Is the warp a signature of interaction with any of the Milky Way’s satellites? How does the gaseous warp couple to the outer stellar disk? Is the gas in the Milky Way lopsided and what can we learn from this about interactions and/or accretion?

This conference will bring together world leading experts in galaxy dynamics, and cosmology in order to promote collaborative efforts across theoretical, computational and observational disciplines to try to answer to these questions. The interpretation of survey data, like SAMI, CALIFA, and MaNGA will be mature, and large sets of data will be also available from instruments such as ALMA and SKA. Cosmological simulations such as the EAGLE and ILLUSTRIS projects are just starting to produce large volumes of the Universe with realistic galaxies, and recent advances in MHD schemes are capturing the gas physics in unprecedented detail. The new simulations expected between now and 2017 will uncover new questions and challenges.